Lynn Donelson Wright

Promoting Resilience of Tomorrow’s Impermanent Coasts

There are three categories of actions that humans need to take in order to minimize the detrimental impacts of global change on tomorrow’s coastal systems. The first, of course, is to cause less harm by reducing our carbon footprint and ceasing to do destructive things like polluting, dredging, severing sediment supply, withdrawing groundwater, overdeveloping etc. Much has been written and spoken about this even though we have said relatively little about it in this book. The second category of actions, which has received minimal attention from the popular media but has been the motivating theme of this book, involves promoting deep enough understanding of the myriad complex interconnections of coastal processes to allow long-term predictions of what may lie ahead. Such predictions are essential to evolving effective strategies for adapting and remaining resilient. The third action is to ensure that to the extent possible we embed coastal science, including matters related to future impacts of climate change, into state and federal policies and law. The aim must be to ensure that regional coastal strategies are based on the best available science to reduce risk to built and natural assets from the adverse effects of short-term practices driven by local vested interests.

Coastal Morphodynamics and Ecosystem Dynamics

The shape of the land and the processes that mold the land are mutually interconnected and change together as a complex system. The coupled suites of mutually-inter-dependent hydrodynamic, biologic and anthropogenic processes, seafloor and landscape morphologies interact to cause time-dependent sequences of change. In many cases it is moving water or air (currents, waves, winds) that redistribute the material. The new land configurations in turn then alter the directions, intensities and gradients of the moving water or air. In other cases, it is biological rather than physical processes that build or degrade morphologic features such as coral reefs or coastal marshes. There is constant feedback among the multiple components of the system.

Coastal Erosion and Land Loss: Causes and Impacts

The margins of the sea are encroaching landward throughout most of the world. This is happening not simply because of sea level rise but also because the solid material- sand, mud, gravel-composing the shore and the subaerial and subaqueous lands immediately adjacent to it is being displaced. In addition to physical erosion by wave, thermal erosion in the Arctic and loss of wetlands through ecological processes are also active. The expected rate of sea level is predicted to exceed critical “tipping points” for wetlands destruction in many regions.

Sea Level Rise: Recent Trends and Future Projections

Seas are rising and seriously impacting coasts and coastal communities globally. Global warming is causing melting of glaciers and steric expansion of water volume. Locally and regionally, other effects including land subsidence and the slowing of ocean currents such as the Gulf Stream are causing additional rises. By midcentury, relative sea levels in cities like New York and Miami may exceed those of the year 2000 by up to 1.2 m (~ 4 ft.).

Complex Intersections of Seas, Lands, Rivers and People

River deltas were the cradles of early civilizations and are currently the habitats of 500 million people. But river deltas worldwide are sinking and being invaded by rising seas. The effects of sea level rise and floods are greatly exacerbated by subsidence and human modifications including reductions in supply of sediment and the extraction of water, oil and gas from deltaic sediments as well as damaging engineering works.

Coastal Systems in the Anthropocene

People are integral parts of nature and, in many respects, are becoming dominant parts. This notion is implicit in the term “Anthropocene”. In no environment is the connection between people and nature more apparent than in coastal systems. Mutual causality between humans and nature plays out there on a daily basis, sometimes in very positive ways and other times in tragic ways. The enjoyment of coastal beauty and spiritual stimulation are among the positive attractions as are access to global seaways, fisheries and recreation. Death, disease and destruction wrought by severe storms and tsunamis are paramount among the downsides. But for a multiplicity of reasons, roughly half of the world’s 7 billion people live within 100 km (60 miles) of the shore. And the activities of those who live much farther inland, for example within the catchments of large rivers that run to the coast, impact the coastal environment and its residents in numerous ways. Human activities that directly impact coastal systems include urbanization, agriculture, nutrient runoff, engineering works, fisheries, oil and gas production, dredging and various forms of pollution. Natural processes that impact coastal residents include sea level rise, storms and storm surges, water-borne pathogens, tsunamis, and loss of ecosystem services. Important ecosystem services include pollination, decomposition, water purification, erosion and flood control, carbon storage, and climate regulation.

The Alaskan Arctic Coast

Near-surface air temperatures in the Arctic are rising 2 to 3 times faster than are temperatures elsewhere on the earth’s surface. In the near future, the Arctic ocean is likely to become ice free in the summer. While this may be good from the perspective of navigation, it is bad from the perspectives of the unique Arctic ecosystem and Native Alaskan subsistence, health and culture, which are tightly bound to, and dependent on, a frozen ocean and frozen permafrost on land.

Coastal Complexity and Predictions of Change

Most people tend to think of coasts as material “things”. What you see when you look at a coast at any instant in time may be a beach composed of sand or a coastal wetland consisting of vegetation, mud and crabs and perhaps some methane or hydrogen sulfide gas. But in previous times it may have been very different and it probably will be different in the future. In reality, coasts are not “things” but processes; they are not static but are constantly becoming something new. This has always been the natural way with coasts. The ever-changing coastal process involves the interplay of solid material (e.g., sand and mud), chemistry (e.g., the pH of the Earth’s oceans), forces, energy fluxes and transfers (e.g., physical, chemical, biological, and solar), biological activity and ecological evolution, and, now, profound human interaction. We may reasonably expect coastal change to be accelerated in response to the climate changes that are now underway in the Anthropocene, a new geologic epoch in which human activities are causing profound and enduring modifications to the earth’s surface.

Future Societal Vulnerability, Risk and Adaptability

It is imperative for humanity to anticipate and plan better for the future impacts of climate change and coastal flooding on low-income, elderly and infirm communities living in flood-prone areas. As sea levels rise, low-lying vulnerable urban areas throughout the world will be more frequently flooded by storms. Low-income families will be forced to move into higher density areas or to low-lying, flood-prone areas. There is growing vulnerability of impoverished people living coastal cities, particularly coastal megacities, to the impacts of climate change. Education and awareness along with regionally specific adaptive management policies are probably the most effective tragedy preventers.

Impacts of Coastal Waters and Flooding on Human Health

Floods are among the most common natural hazards with complex and far-reaching impacts. Coastal floods are most often caused by storm surge (coastal), rivers that exceed their flood stage capacity (fluvial), and torrential rainfall (pluvial). Increasingly, compound flooding by all three causes is the most severe. The adverse consequences of flood events, especially coastal flooding, to human health. Drowning is the major cause of death, followed by heart attacks, hypothermia, blunt trauma caused by wind-borne objects and vehicle-related accidents. Snakebites, electrocution and wound infections are also causes of death. Less obvious health impacts involve diseases and toxins spread by water and water-nurtured vectors (e.g. mosquitos).